I find it somewhat amazing all the "ifs" and "mays" and other similar qualifiers for advising the OP dump his current 2 x 16GB sticks and put them on a shelf to collect dust and spend even more money for 2 x 32GB sticks.
For example (just to illustrate, not to point fingers at anyone),
The issue with just adding another set (especially after some time has passed since you got your original kit) is the vendor may have changed the underlying IC's without changing the model number. So in going this route you may encounter compatibility issues.
While technically true, the real facts are, and the most likely outcome is the two new sticks will play perfectly well with the first two - with proper homework before buying, of course.
Contrary to what some still
apparently firmly believe, RAM manufacturing technologies and techniques have improved
tremendously over the years. In years past (many years past), for example, manufacturers used to test every stick before leaving the factory to ensure it worked
AND met published specs. Even further, they used to test and pair matching sticks together just to ensure compatibility. Then they packaged the matched sticks together so they could then market them as "dual-channel" kits.
Fast forward 10 - 15 years or so and not only have we (humans) learned to produce the raw materials used to make memory chips as pure and imperfection-free as humanly possible (without divine intervention), we have also learned to use those materials to produce memory modules that adhere to published specs just as precisely.
This insures the specs of each stick coming off the assembly line is so close to published specs, within such tight tolerances, manufacturers no longer need to test each stick for accuracy. And they no longer need to test and match pairs for dual (or triple or quad) channel. They still pair, package and market them as dual-channel kits, but that is for marketing and logistics (inventory, shipping, etc.) reasons only - not compatibility.
Not only that, because Samsung and Micron and the other IC makers have learned to so precisely produce ICs to published specs, we (consumers) don't even have to make sure we pair RAM with the exact same brand and models numbers like we used to.
Why?
Again, because they manufacture so precisely to published specs. BUT ALSO, contrary to what some
apparently want us to believe, motherboard, CPU and memory controller manufacturers have not been sitting on their thumbs the last 10, 15+ years either. Memory controllers have significantly improved such that they are very capable of enabling sticks with
slightly different deviations from the published specs to work just fine together - even in dual, triple or quad channel.
Are there exceptions? Of course! Until Man can create perfection 100% of the time, there will always be exceptions. For this reason, I still recommend using matching sticks for each pair whenever possible. But odds are greatly in the user's favor that when adding a second pair, as long as the published specs are compatible with the board, they will work just fine - even if different speeds, model numbers and even brand. The system will simply toggle down to the slowest speed, most likely with no problems whatsoever.
Note this is why, for years now, it has not been necessary to buy RAM that is listed on the motherboard's QVL. We have only needed to buy RAM that matches the specs of listed RAM to ensure compatibility.
We've done it dozens of times here - even mixing a pair of Crucial with a pair of Corsair, and Corsair with Kingston, and other combinations with no compatibility or stability issues at all.
One significant disclaimer - we use default settings and we make sure the specs match specs of RAM listed on the motherboard's QVL. If doing extreme overclocking, I still recommend buying all identical RAM you think you will ever need (or want) at once. And by extreme, I mean when using "custom" settings - and not one of the preset options provided by many motherboard makers through the BIOS Setup Menu.
So yes, there are some "ifs" that "may" cause problems when using 4 sticks instead of 2. But I contend that is more likely to happen on cheap motherboards from manufacturers nobody has ever heard of, using cheap sticks from RAM makers that nobody has heard of either.
@inquisitor1 - you can go out to the Crucial site and run their
system scanner. It will scan your system then provide a list of compatible RAM. You do NOT have to buy Crucial. You can go with another brand with the same specs as Crucial's and feel confident it will work.
HOWEVER, if you buy listed Crucial RAM directly from Crucial, they guarantee compatibility. And last time I bought directly from them for my laptop, it was actually $10 less than Amazon was selling the exact same Crucial RAM!
Yeah, I would have got free shipping from Amazon but the $10 savings made up for that - and yes, the added Crucial RAM worked perfectly fine with the exiting Hynix RAM that came with the laptop - and in Dual channel mode too.